Cold-blooded animals regulate their body temperature through the environment, while warm-blooded animals use internal mechanisms. Warm-blooded animals require more food. The terms “cold-blooded” and “warm-blooded” are misleading. Most mammals and birds are warm-blooded, while most reptiles, fish, insects, amphibians, and arachnids are cold-blooded. Warm-blooded animals need more food, but have increased stamina. Cold-blooded animals can rely on environmental factors for heat and have different sets of enzymes for biological processes.
Cold-blooded animals are those whose body temperatures are regulated by their environment, and warm-blooded animals are those whose body temperatures are kept relatively constant by internal mechanisms. Along with how their body temperatures vary, another major difference between these types of animals is that warm-blooded animals require more food. The terms “cold-blooded” and “warm-blooded” are misleading because the blood of cold-blooded animals is not necessarily cold, it just varies according to the temperature of the environment. More precise terms are “ectothermic” instead of “cold blooded” and “endothermic” or “homeothermic” instead of “warm blooded”. Another term for ectothermic animals is “poikilotherms,” which means animals that have varying body temperatures.
Examples and exceptions
The vast majority of mammals and birds are warm-blooded, and nearly all reptiles, fish, insects, amphibians, and arachnids are cold-blooded. There are some exceptions though, and some animals that have characteristics of both types. For example, bats and moles are mammals, but their body temperatures can vary depending on their environment, especially when they are not active. Some insects, such as hawk moths and some bees, can raise their body temperature by flapping their wings. Some fish have internal mechanisms that help keep their brain and eyes from getting too cold, which could impair their function.
Dietary requirements
A significant difference between warm-blooded animals and cold-blooded animals is that warm-blooded animals typically need three to ten times as much food to survive, because they have to create their own body heat. Consequently, these endothermic animals must be three to ten times better at obtaining food, placing them on a different metabolic and evolutionary level. Ectotherms can rely on sunlight and other environmental factors to provide heat, rather than having to create it themselves, so their bodies need less food.
Some advantages and disadvantages of each
There are several benefits to being endothermic: increased stamina, having only one set of bodily enzymes that function optimally at a set temperature, and the ability to raise body temperature during frigid weather. A spider caught in a blizzard will freeze, but a human has at least a chance of survival. Ectothermic animals need to maintain different sets of enzymes for their biological processes because enzymes are sensitive to temperature, but endothermic animals can maintain one set.
The most useful benefit of being endothermic is increased stamina. An endothermic creature can outrun a cold-blooded predator as long as it avoids the initial attack. Warm-blooded predators can outrun their ectothermic prey and endothermic animals can feed for a longer time. Some people might argue that endothermic creatures are superior because they tend to have more stamina, but can’t move as fast as cold-blooded animals for short bursts, and starve much more easily than ectothermic creatures.
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